Echo recording apparatus



Mud! 30, R. L. HOLLINGSWORTH 2,075,;28 5

ECHO RECORDING APPARATUS 'Filed Oct. 1, 1934 HYDRO/"Hm? ("1a was-474's)? 1 dbl/1V0 war; asavawnvm a INVENTOR R.L;HOLL|N6SWORTH BY V ATTORNEY Patented Mar, 30, 1937 ATE T OFFICE 2,075,235- .Ecnomicoannto APPARATUS fit. Lee ,Iiollingsworth", :Riverhead, N. Y., assignor to RadiotCorporation of America, a corporation r of Delaware minaret amber 1, 1934, Serial No. 746,359

romm. (01. 177-236) This method of .echotime recording is adapted to be used to recordsthe timevrequired for -a sound wave to travel from any sourcetoareflecting object and, back-to said source. The

method and means ,ofthe presentinvention is particularly adapted to usewon ships at sea, for

measuring the depth of 'water inwhich the ship islocated. a 1

In its broadest aspect, my method and means 10 for a measuring distanceby recording time in which a sound wave traveling. between two points comprises a means of supplying to a re-'- oorder aconstantnumber of electrical impulses per second through a vacuum tuberelay, and

- means for sending out sound waveselectrically.

The transmitted sound wavesare recorded at the instant of transmissiomand the echo of the sound wave or signal picked up by hydrophones and superimposed or recorded in tandem with the recordingof theconstant impulses provides asimple and accurate means of calculating the depth of the water by using the constant; recorded impulses as a time constant for measuring purposes. The invention is ofwide application andmay be 25 used on aircraftgsuch as dirigibles and airplanes, for measuring the distance between the same and earth or any refiectingobject,

The: novel features of my invention have been pointed out with particularity in the claim ap- 30 pended hereto. j l v c The following description, together with the single figure in the drawing, explains the working principles of this system. The drawing is utilized for purposes of illustration only and is not, intended to limit my invention to any particular circuit since obviously many departures from the circuit arrangement shown may be made without departing from the spirit of the invention. A 40 In the drawing: l is a hydrophone'located at an appropriate position on the hull of the ship. The hydrophone is asshown coupled to a vacuum tube amplifier 2, which excites the rectifier stage 3. The output of the rectifier stage 3 is connected 45 as shown, so that current therein flows to ground G by way of resistance 4. A tuning fork 5 supplies exciting energy at a constant frequency, say of 110 cycles per second, to a thermionic amplifier .6 of the vacuum tube type, which in turn 50 supplies energy to the input circuit of a second thermionic rectifier 'l, the output of which is completed to ground by way of a resistance 4 so that current flowing in the output of the rectifier. 'l i must pass through the resistance 4. alternator ll delivers a desirable'frequency for submarine signal work, or a frequency desirable for distance measuring from aircraft, to transformers l5, l6 and 20. Transformer I6 is supplied with power from source l4 when the key If is closed, which in turn supplies exciting ener- 5 gy of the desired frequencyrto the sound wave transmitter I9, byway of the driving or exciting coil l8. Transformer 15 supplies the alternator energycontinuously to thegrids of the tubes in a vacuum tubeprelaying stage l3. The control 10 grids of the tubes in stage 13 are biased by source I! connected as shown, and a potential drop through resistance H, derived in a manner:

which appears hereinafter in detail to a point at which the tubes are normally cut off ornon- 15 conductive; 1

The thermionic tube 8, which has been termed the keyer tube, has its control grid biased positive'by means of a source 9 to a point at which current supplied by the source l0 normally flows between the anode and cathode of 8 by way of the anode circuit, including the source Ill, resistance II and ground G. The potential drop produced in I l by this current when added to the negative potential supplied by l2 to the control grids of the tubes in stage 13, biases said tubes to cut ofi, as stated above.

In describing the operation of the system, let us assume that thekey I1 is closed and the sound transmitter l9 sends out sound waves. This energy is picked up by the hydrophone I direct and is amplified in the thermionic amplifying stage 2 and rectified in 3 and passes to ground through 3 and resistance 4. Vacuum tube keyer B has a positive bias applied to its grid by battery 9 and normally draws plate current from the source In. As the rectified signal passes through resistance 4 a negative voltage produced in 4 counteracts the positive grid potential supplied by 9, thereby cutting oil. or lowering considerably the plate current in the tube 8. This tubethen becomes substantially non-conductive and the current ceases to flow from the source I0 through the tube to ground. When the plate current through 8 is cut off, no current flows in resistance II and the 5 voltage drop through ll falls to zero, allowing bias from the source l2 alone to be applied to the relaying amplifying stage l3, which is normally blocked when 8 is drawing plate current.

Consequently, the incoming signal received on hydrophone l directly from the transmitter l9 reduces the negative bias of the grids of the tubes in stage l3, allowing excitation of the grids of the tubes of stage l3 by source of energy I! through transformers l5 and 2|. This amplifledand repeated energy from I4 in turn energizes the winding on the recording armature 24 which is placed in the strong magnetic field produced by field coil 22; 2| is the battery supply for 22 and the anode 5 supply for the tubesof stage I3; 23 is a resistance in circuit with the winding 22 to protect the same against short circuiting.

The impulses from thetuning fork 5 reach the winding on the recording armatureZd by way 0 of thermionic amplifier 6, rectifier 1, resistance 4, keying stage 8, and amplifying relaying stage IS, in the same manner in which the energy from I 4 reaches said armature, as described above, when stage I3 is rendered conductive on the reception of an echo of the transmitted signal. In

other words, when the tuning fork starts operating, energy is impressed on the rectifier I and direct current components passing through the resistance 4 counteract the effect of source 9 on the grid of tube 8, which is normally conductive,

to render the same non-conductive, thereby reducing the potential drop through 'II and consequently increasing the conductivity of the'tubes in stage l3. In this manner, the energy from the tuning fork 5 operates the armature 2'4 continuously at 110 impulses per second.

Now, for the reasons described above in detail, when the key N is pressed a dash is made instantly on the recording apparatus. The sound which has been recorded also travels to the bottom of the body of water or to earth from an airplane or to some reflecting object, and is reflected back to the hydrophone I. This echo passes through the amplifier 2 and rectifier ,3 and 0p- 3 crates as set forth in detail to recordan impulse by way of the recording apparatus 24, 25. Now,

if the number of impulses recorded in response to the vibrations of the tuning fork be counted between the recording of the transmitted signal and the recording of the echo of the transmitted signal, the depth of the water in which the boat is located or the distance from the aircraft to earth or other reflecting object may be calculated immediately. In calculating the distance it may be assumed'that sound travels through water at about 4,400 feet per second, allowing 20 feet for each of the tuning fork impulses.

I claim:

A distance measuring device comprising in combination a source of wave energy, means under control of said source for transmitting sound signals at the frequency of said wave energy, means including receiving apparatus for detecting said sound waves at the moment of transmission and also at the moment of reception after reflection from a remote object, means for translating the detected sound waves into electrical waves, a source of electrical oscillations of predetermined frequency, means for combining in one circuit the electrical waves corresponding to the sound waves and the oscillations of said predetermined frequency, an impedancenetwork adapted to 'be rendered conductive in response to the translation of said sound waves into electrical waves and a recording apparatus operable under control of 'impulses from said impedance network for indicating elapsed time between the moment of sending and the moment of receipt after reflection of a given sound wave, said elapsed time being measured in terms of wave cycles of said source of electrical oscillations. V

R. LEE HOLLINGSWORTH. 

